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Title: Activation of the yeast exosome complex
Author: LaCava, John
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2004
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This study concentrates on structural and functional analysis of the S. cerevisiae exosome complex. It is likely that these exoribonucleases are in a complex in order to inhibit potential non-specific activities of the individual components. In this way a potent but highly specific RNA degradation machinery is maintained. This model is supported by the lack of free components in vivo and the relatively low enzymatic activity in vitro of the purified exosome complex. This study shows how the exosome can be stimulated into a highly effective and processive activity in vitro by incubation of purified exosome preparations with an activating complex that contains three proteins Mtr4p, Air2p, and Trf4p. Mtr4p is an essential nuclear RNA helicase previously reported to be required for nuclear exosome activity. Air2p is a RING-type Zink-finger protein. Trf4p is shown to be a poly(A) polymerase. The Mtr4p/Air2p/Trf4p polyadenylation complex (MATPAC ) is responsible both for the polyadenylation of target RNAs prior to degradation and the facilitation of the processive exosome mediated degradation. Genetic analyses of trf4. and air2. mutations support these in vitro findings. In addition to the stimulation of exosome by the MATPAC complex, this study also presents evidence for a distinct activation mechanism. This involves ADP and inorganic phosphate, strongly indicating that one or more of the phosphorolytic activities has been stimulated. Lastly, through a collaborative effort we have sought to obtain high-resolution cryo-electron microscopy data in order to further characterise the global structure of the exosome and identify the positions of individual components.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available